<!DOCTYPE html>
<html lang="zh">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style type="text/css">
        div{
            width: 100px;
            height: 100px;
            border: 1px   solid  red;
            /*margin: 10px;*/

           /* margin-top: 10px;
            margin-right: 10px;
            margin-bottom: 10px;
            margin-left: 10px;*/

            /*margin: 10px 20px;*/
            /*margin: 10px 20px 30px;*/
            margin: 10px 20px 30px 40px;
        }


    </style>
</head>
<body>
<div>
    我是div里的内容！
</div>

</body>
</html>